1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor laser diode (hereafter denoted as LD), in particular, the invention relates to a method to form a dulled side surface of an opening to provide an electrode of the LD.
2. Related Background Art
A Japanese Patent Application published as JP-2003-298190A has disclosed an LD with the ridge waveguide structure. Such an LD with the striped structure like the ridge waveguide often causes damage to the striped structure during the process. Accordingly, the LD disclosed therein has provided a pair of protrusion with a height greater than a height of the ridge in both sides of the ridge. The protrusion provided in both side of and apart from the ridge may operate as a protection means for the striped structure.
However, the protrusion structure is necessary to carry out several process steps, namely, first forming a patterned photo-resist by the lithography and subsequent etching to form the protrusion. Moreover, when the protrusion is formed before the formation of the striped structure, the protrusion with the height greater than that to be formed for the striped structure sometimes influences patterning of the photo-resist for the striped structure. The photo-lithography for a bumpy surface sometimes upsets the preciseness of the photo-resist pattern. A modified process for an LD has been suggested, in which a resin with low viscosity buries the striped structure and forms a planar top surface thereof. The planar resin layer may effectively protect the striped structure.
In such a planar structure by the resin layer, an electrical contact to the active portion of the LD is realized by forming an opening in the resin layer in a top of the striped structure. However, the planarization by the resin is necessary to form the resin thick enough, which results in a deeper opening and causes a breakage of the wiring to the active region of the LD at a corner of the opening in the thick resin.